ABSTRACT Objective: To analyze spirituality in the process of illness uncertainty in cancer patients. Methods: This is a qualitative study, in which Merle Mishel’s Theory of Uncertainty of Disease was used as a theoretical framework; and as a methodological reference, the stages of Bardin’s Content Analysis. As a technique for obtaining information, a semi-structured interview was used. Results: Spirituality in the uncertainty of the disease varies from patient to patient and acts in a unique way. They presented readaptation attitudes in their reports. The presence of spirituality in their lives acted as the main force mechanism to deal with the uncertainty of the disease, and this moment was called by Mishel “probabilistic thinking”. Conclusion: Patients demonstrated readaptation attitudes in their reports, and spirituality acted as the main mechanism of strength to deal with uncertainty in the disease